Blown voice coil?

I've noticed recently, I don't know when it happened exactly, that at certain frequencies one of my PSB Century 500i's 'flutters', sort of like a rattling noise like the driver is bottoming out. It's only with the one speaker and it's only at certain frequencies (probably somewhere between 500-1500).
If this is a blown voice coil and the driver has to be replaced (most likely), does anyone know if it is possible to simply buy a new driver from PSB (the speakers are past warranty) and have it shipped to me so I can replace the driver myself? The speaker right now is still usable and I don't want to be without it for 2 weeks while it gets fixed.

Lawrence, I am going through the exact same thing right now with a pair of Totem Arro floorstanding speakers. I started a thread about it at the end of last week. Here is a link to that thread so you can see what happened in my case:http://www.hometheaterforum.com/uub/...ML/044406.html
One speaker is having a problem like what you describe at very low frequencies. As I said in the above thread, I have only observed the "fluttering" of the driver of one speaker during one passage of one song. Nevertheless, the speakers are at the dealer awaiting a new driver from Totem. A technician at the store is going to swap out drivers as soon as the new one arrives. He said I blew a voice coil. I suppose if you are knowledgable in this area, you could replace the driver yourself. However, I am not sure how speaker manufacuturers handle these things. They may refer you to an authorized dealer for the repair.
Once I get the speakers back, I am going to add a sub to my system to prevent this from happening again. Good luck.
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